A breathing apparatus of this type is disclosed in German Utility Model DE-GM 80 15 449.
This publication describes a breathing apparatus in the form of an emergency filter apparatus with a protective hood. The filter apparatus contains a combined submicron particulate and carbon monoxide (CO) filter with an air inlet opening and an air outlet opening.
The air outlet opening is surrounded by a half-mask to which a protective hood is attached. In the position ready for use, the air inlet and air outlet openings are each closed with a stopper to protect the filter material from damage, or to prevent impairment by humidity of the catalyst in the CO filter which is required for filtering carbon monoxide. For use, the emergency filter apparatus is removed from the housing, and during this removal, both stoppers are loosened from the respective air pass-through openings.
Other breathing apparatus include a cartridge for processing the breathing gas and this cartridge is filled with a chemical that binds carbond dioxide (CO.sub.2) and gives off oxygen. In these apparatus the entire housing is sealed in an air-tight manner. At a suitable location on the housing, one that is visible to the wearer, a container having moisture-sensitive material is attached, by means of which the tightness of the supporting housing can be monitored. In this connection, reference can be made to published German patent application DE-OS 19 61 910.
The prerequisite for a reliable and accurate indication by the moisture-sensitive indicator is that the housing in which the breathing apparatus is located is sealed in an air-tight manner. For this purpose expensive sealing and fastening elements are required.